1. Field of the Invention
The present invention relates to a particulate matter concentration measuring apparatus configured to measure a concentration of particulate matter (PM) in exhaust gas.
2. Description of the Related Art
FIG. 1 of European Patent Application Publication No. EP 1916394 A1 discloses an apparatus 20PM (PM Sensor) which is known as a conventional apparatus for detecting a concentration of particulate matter primarily of C (carbon) in exhaust gas from diesel engines. This particulate matter concentration measuring apparatus 20PM includes a secondary exhaust line 21A diverging from an exhaust line 21, a particulate matter detection filter 22A provided in the secondary exhaust line 21A, and a differential pressure measuring part 22B that measures a differential pressure ΔP caused between the inlet and outlet of the particulate matter detection filter 22A. Further, a flow rate measuring part 24 and a temperature measuring part T1 are provided in the secondary exhaust line 21A, and a heater 22H is provided in the particulate matter detection filter 22A.
In the conventional particulate matter concentration measuring apparatus 20PM according to European Patent Application Publication No. EP 1916394 A1, the differential pressure ΔP across the particulate matter detection filter 22A, the temperature T of exhaust gas in the secondary exhaust line 21A, and the flow rate Q2 of the exhaust gas in the secondary exhaust line 21A are measured. The mass of the particulate matter trapped with the particulate matter detection filter 22A per unit time, PM [g/h], is calculated from the measured differential pressure ΔP, exhaust gas temperature T, and exhaust gas flow rate Q2. The concentration of the particulate matter in the exhaust gas, PMconc [g/m3], is calculated from this mass of the particulate matter, PM [g/h].
Further, European Patent Application Publication No. EP 1916394 A1 describes a diesel particulate filter (DPF) 22 formed of porous ceramic and provided in the exhaust line 21 as part of a conventional exhaust gas purifying apparatus 20. The secondary exhaust line 21A of the conventional particulate matter concentration measuring apparatus 20PM is connected to the upstream side of the diesel particulate filter 22 in the flow of the exhaust gas. The mass of the particulate matter flowing into the diesel particulate filter 22, PMenter full filter [g/h], is calculated from the determined concentration of the particulate matter in the exhaust gas, PMconc [g/m3], and the engine operating condition or the flow rate of gas flowing into the diesel particulate filter 22 in the exhaust line 21, Q1.
The entire contents of European Patent Application Publication No. EP 1916394 A1 are incorporated herein by reference.